This invention relates to gas fired broiler ovens for the cooking of foods, and is characterized by the use of direct radiation of heat into the food substance, as distinguished from conduction and/or convection heating. Another characteristic feature of this invention is the use of a transparent liner that transmits radiant heat and protects the gas fired radiant burners disposed both above and below the food substance. Accordingly, it is a general object of this invention to cooperatively employ gas fired radiants and protective transparent liners in an oven for food processing, and more particularly in a broiler oven that subjects food substance to both top and bottom radiant heat.
Heretofore, the gas burners of broilers have been exposed to drippings and splatterings, and the standard broiler has had an upper burner only, and a drip pan beneath a food supporting rack, whereby the upper face only of the food is subjected to the burner flames; which chars the food and requires a turn-over of the food in order to subject the other side thereof to the burner flame. It is an object of this invention to eliminate the subjection of foods to the burner flames, and to protect the burner (radiants) from food drippings and splatterings. Consequently, it now becomes a practicality with this invention to employ both top and bottom burners and particularly radiant burners of the type employed herein; in a broiler oven and in close proximity to the food being processed.
Gas fired burner radiants are widely used and are successful in many practical installations, where radiant heating is desired, as distinguished from conduction and convection heating. The advantage of radiant heating is that it is direct and usually more economical. However, such radiants are comprised of a multiplicity of very small combustion holes that are adversely affected by food drippings and splatterings. Consequently, gas fired burner radiants have not been successfully employed within broiler ovens and the like. However, radiants of the type under consideration reach a high surface temperature, they have a high rate of heat-up, as well as a fast cooldown rate, and their carbon monoxide (CO) emissiom is almost non-existant, while the products of combustion are CO.sub.2 and H.sub.2 O. The great advantage of these radiants for food processing is that their surface temperature is coextensive of the radiant surface at a known value, of 800.degree. F. to 1600.degree. F., and the fact that the effect of the radiation travels at the speed of light and diminishes with the cosine of the angle to the plane of the radiant surface and at a rate determined by the square of the distance from said plane. This invention deals specifically with radiant infra-red light lying outside the visible spectrum at its red end; a thermal radiation of a wavelength longer than those of visible light. It is therefore an object of this invention to advantageously employ the light characteristics of infra-red heat radiation in a broiler oven by utilizing transparent walls or liners therein.
The interior walls of ovens and broilers have been glazed or porcelainized. However, glass per se has not been used as walls over and/or under gas burners in an oven or broiler to isolate the flames from the food. That is, the prior art broiler ovens do not protect the burners while permitting them to radiate heat. Consequently, the burners become fouled with drippings and splatterings from the food processed. And, until recently there has been no transparent material which could be closely juxtaposed to an open flame without its destruction thereby. However, there is now available a "transparent glass-ceramic" that resists temperatures to 1470.degree. F., a material with virtually zero thermal expansion and sufficient mechanical resistance as required for normal structural applications. Such a material is "ROBAX", a trademark, manufactured by Schott Glaswerke in Europe, and available from Schott America and its authorized dealers. It is an object of this invention to combine gas fired infra red radiants with light transmitting glass-ceramic liners in an oven broiler, whereby the food substance processed thereby is subjected to direct radiant heat.
Gas fired broilers and ovens necessarily involve the intake of air and the discharge of the products of combustion, and all of which results in convection flow thereof (forced or natural). It is an object of this invention to isolate the gas fired flow of gases from the cooking chamber, while venting the cooking chamber for the discharge of vapors developed as a result of high heat application to the food. With the present invention, there is a flue whoe's primary function is to discharge the products of combustion, and this flue also discharges the food vapors which are generated. In practice, the food processing chamber can be relatively small for specialized food processing, and is essentially a front opening tunnel vented at the rear to the aforesaid flue.
Broiler ovens are usually of rectangular cross section, having an interior comprised of top and bottom and opposite side walls. The broiler oven herein disclosed has top and bottom radiants, in which case there are top and bottom transparent walls isolating said top and bottom radiants from the food chamber. However, this arrangement is not to preclude side radiants in a larger broiler oven or the like when there are also side walls to isolate the side radiants from the food chamber. Therefore, it is an object of this invention to protect any and all radiants of an oven by isolating the same from the food chamber by means of transparent light transmitting walls; that is walls transmitting radiant heat energy and particularly infra-red light waves that directly heats the body of substance upon which it impinges.
Cleaning is an ever present problem with broiler ovens and the like, and the interior walls are usually coated metal which can be wiped clean and/or subjected to harsh cleaners. It is an object of this invention to provide a broiler oven interior which is inherently easy to cleam. With the present invention the glass-ceramic liner or liners are smooth with the hardness of glass or ceramic, and from which drippings and splatterings burn or brush off, or are readily wiped away. Cleaning is also facilitated by easy removal or replacement of the glass-ceramic walls in the form of panels or tiles.
Heretofore, screens have been used to bounce back a percentage of the infra-red waves, thus raising and maintaining the radiant temperature desired. Accordingly, it is an object of this invention to reflect a percentage of infra-red waves from the inside of the glass-ceramic wall or liner which is suitably spaced at an optimum distance form the radiant, thereby maintaining the desired radiant temperature. Therefore, a small amount of reflected light enhances radiant operation, while the greater amount of radiant light is transmitted through the glass-ceramic; and to this end the transparency of the glass-ceramic is selected as may be required.